Lecture 27-cwo-fisheries

Lecture 27-cwo-fisheries - Outline: 1. Fisheries (insights...

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1. Fisheries (insights from simple models) 1. Maximum sustained yield 1. Challenges of MSY 1. Alternatives Outline:
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Fisheries: Thousands of tons 0 100 200 300 1968 1978 1988 1998 Cod spawning pop., North Sea
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Fisheries: Why do fisheries collapse? Can we understand collapses from simple population models? Do models suggest any improvements?
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Logistic growth: Without harvest: dN/dt = rN(K-N)/K With harvest quota: dN/dt = rN(K-N)/K Y What is the Maximum Sustained Yield? What are the dynamics?
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MSY: 0 25 50 75 100 Population size, N Population growth, dN/dt How do we figure out MSY? Talk to your neighbor…
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Population trajectory: 0 25 50 75 100 0 50 100 150 200 250 300 350 400 Time (years) Abundance No harvest Harvest at MSY What if we harvest at slightly above MSY (+4%)?
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Population trajectory: 0 25 50 75 100 0 50 100 150 200 250 300 350 400 Time (years) Abundance No harvest Harvest at 1.04*MSY Harvest at MSY What if we harvest at slightly below MSY (-4%)?
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Population trajectory: 0 25 50 75 100 0 50 100 150 200 250 300 350 400 Time (years) Abundance No harvest Harvest at 1.04*MSY Harvest at MSY Harvest at 0.96*MSY
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0 25 50 75 100 Population size, N
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Lecture 27-cwo-fisheries - Outline: 1. Fisheries (insights...

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